1. Field of the Invention
The present invention relates generally to orthotic devices, and more specifically to knee braces for, for example, supporting ligament instability and/or treating patellofemoral dysfunction.
2. Description of the Related Art
Many orthotic devices support and/or protect the joints of the human anatomy, such as the knee joint. For instance, a wide variety of knee braces are generally intended to limit unnatural knee joint movement, which is a common source of structural damage to the knee. At the same time, such knee braces preferably allow a natural range of knee motion so as not to impede normal walking, running or other knee movements.
Knee braces are also commonly used to prevent or remediate functional disorders of the patellofemoral joint. The patellofemoral joint of the knee is an articulation between the patella and femur. The joint includes an articular surface on the posterior of the patella and a corresponding articular surface on the anterior of the head of the femur that is termed the trochlea. The posterior of the patella is contoured as a ridge, while the trochlea is contoured as a groove that is dimensioned to receive the patellar ridge in a complementary manner. In a healthy patellofemoral joint, the patellar ridge accurately tracks the underlying trochlear groove as the knee is moved through flexion or extension.
The patellofemoral joint is subject to a wide variety of functional disorders that adversely affect the joint operation. Less severe forms of patellofemoral joint disorder cause pain in the joint, but do not exhibit errors in patellar tracking of the trochlear groove. In more severe forms of patellofemoral joint disorder, patellar tracking errors are evident in addition to joint pain, but there is no subluxation or dislocation of the joint. In still more severe forms of patellofemoral joint disorder, patellar tracking errors result in subluxation or dislocation of the joint. Recurrent subluxation of the patellofemoral joint is a particular disorder whereby the patella deviates transiently and typically rapidly from its normal axis of movement due to patellar tracking errors during movement of the knee. Slight deviations of the patella from its normal axis of movement are termed minor subluxation and often do not produce clinically apparent relocation of the patella. Minor subluxation is often the result of a functional imbalance in the knee. Significant deviations of patellar movement that approach dislocation are termed major subluxation. In certain instances, major subluxation is induced by strenuous activity, although it often occurs even in the absence of such activity. Recurrent patellar subluxation, both major and minor, is a relatively frequent condition among females generally and among female athletes in particular.
Many instances of subluxation or dislocation of the patella due to patellar tracking errors are in the lateral direction because biomechanical forces typically bias the patella laterally when the knee is load-bearing. Additionally, subluxation or dislocation of the patella due to patellar tracking errors has the greatest risk of occurring when the knee is approaching extension. Specifically, when the knee ranges between about 30° of full extension and full extension, the trochlear groove becomes relatively small and shallow which is conducive to subluxation or dislocation. Functional disorders of the patellofemoral joint are highly disadvantageous because such disorders often ultimately lead to cartilage damage and arthritis of the knee.